Hydrogen gas is frequently used to cool bearings in gas-fired turbine generators. These generators require periodic service which involves access into the turbine. Prior to entry into the turbine, the hydrogen must be purged. Carbon dioxide is used as an intermediate gas to purge the hydrogen. This prevents direct contact between the hydrogen and air to prevent a combustible mixture of hydrogen and oxygen. Once hydrogen is purged to safe levels, the carbon dioxide is then purged using air. The air provides a safe working environment once oxygen and carbon dioxide meet required levels. When service work is complete, the process is reversed. Carbon dioxide is used to purge the air and then the carbon dioxide is purged with hydrogen.
Bulk liquid carbon dioxide systems can be used as the source when turbines are large enough to justify their expense. These systems are fitted with electric heaters to vaporize the liquid carbon dioxide. Bulk gas sources for carbon dioxide purge gas are impractical for smaller turbine generator facilities due to high cost of refrigeration and storage systems along with loss from vaporization and subsequent venting.
Smaller facilities must utilize high pressure carbon dioxide gas cylinders as their supply source. Purging hydrogen with carbon dioxide from cylinders is currently a manual process that is very labor intensive and slow. Due to the nature of carbon dioxide, withdrawal from the high pressure cylinders often results in freezing of lines, valves and regulators; collapse of the head pressure; and even solidification of the liquid in the cylinders to dry ice. Additionally, the cold liquid or gas coming from the cylinders presents a safety risk for personnel and for supply systems. Some carbon dioxide purge gas systems have been fitted in an ad hoc manner with heated regulators and/or electric heaters, but they are still manual, labor intensive and their operation is frequently interrupted or slowed down for cylinder exchanges.
Cylinder freezing and loss of head pressure slows down the purging process and so it is common that cylinders must be replaced long before they are exhausted. Replacement of cylinders before they are exhausted results in significant gas waste. Extreme cold also damages regulators and regulator failure can result in damage to turbine systems. High pressure can also cause leaks in system seals that would result in direct leakage of hydrogen to atmosphere which is what purging is intended to prevent.
Summarizing the problems in the state of the art processes:                They are labor intense manual operations which frequently requires two to three operators working six to fourteen hours to complete a purge depending on the size of the turbine and outside temperature of the cylinders        Low temperature gas from cylinders resulting in damage to supply system components and turbines        Low temperature and high pressures which present an increased risk of injury for system operators manually exchanging cylinders        Possible loss of individual cylinder head pressure resulting in sublimation of liquid carbon dioxide to dry ice        Significantly longer purge time than bulk systems resulting in extended down time for power units which can lengthen the time a turbine is out of service. This can be both a loss of revenue for the turbine operator and a longer loss of power for energy users supplied by power turbines        
The foregoing represents the state of the art since even before hydrogen cooled turbines became standard. See, e.g., U.S. Pat. No. 3,258,619. The ad hoc augmentation of carbon dioxide delivery with heated regulators and other thermal control elements have had only marginal benefit. In view of the foregoing, there is a clear, long felt need in the art for solutions to address the slow, problematic and gas wasting state of the art.